1. Field of the Invention
The present invention relates to a communication device in communication system and computer network, particularly, to a midplane of a communication device.
2. Description of Related Art
With development of internet, more and more types of services can be supported by internet. At present, internet supports not only services, such as Web Browser Service, etc., but also services with high bandwidth requirements, such as Video Service, Multimedia Service and so on. In order to adapt to development of broadband services, communication device, such as switch, router, etc., which has taken an important position in the broadband equipments in Intranet or Metropolitan Area Network (MAN), are facing a higher demand. With increase of network capacity, a communication device is required to support more ports and have faster port speed, so gross system capacity of the communication device also increases to a range from hundreds of Gbps (Gigabits per second) to several Tbps (Terabits per second), and even would increase to dozens of or even hundreds of Tbps in future.
The growth of the system capacity of a communication device has brought changes in a configuration of the communication device. A multi-plane exchange technology has been used commonly in current high-level communication devices, in which a plurality of exchange-cards work together to complete data exchange between line-cards. In this way, high-speed data links are required to connect each line-card to each exchange-card. The bandwidth of each line-card may reach to dozens or even hundreds of Gbps, the number of high-speed data links from the each line-card to each exchange-card correspondingly reaches to dozens or even hundreds, so the whole high-speed data links of the communication device may reach to thousands.
Since wiring of these high-speed data links is usually disposed in a backplane, very high requirement is made to a design of the backplane. Meanwhile, in order to provide more card slots, a midplane having two sides for inserting cards has become a major choice for large-capacity communication devices. In prior art, two types of midplanes are mainly adopted as follows.
An exemplary structure of a first type of a midplane is shown in FIG. 1, two sides of the midplane 100 are provided with connectors for inserting cards, and the connectors are longitudinally parallelly arranged in general. FIG. 1a is a front view of the midplane 100, two management-card connectors 130 for connecting top-management-card(s) or other management-card(s) are arranged in the middle of one side of the midplane 100, and three interface-card connector(s) 110 for connecting interface-card(s) are arranged at each side of the management-card connectors 130. FIG. 1b is a rear view of the midplane 100, three exchange-card connectors 120 for connecting exchange-card(s) are arranged in the middle of the other side of the midplane 100, and three transaction-card connectors 140 for connecting transaction-card(s) are arranged at each side of the exchange-card connectors 120. FIG. 1c is a top view of the midplane 100, the transaction-card connectors 140 and the interface-card connectors 110 are symmetrically arranged on two sides of the midplane 100, so the transaction-card(s) and the interface-card(s) are respectively inserted into the corresponding transaction-card connector(s) 140 and the corresponding interface-card connector(s) 110 in the manner of mating insertion, so as to achieve the function of line-card(s).
For such a type of the midplane, because the exchange-card(s) is in charge of data exchange between the transaction-card(s) and the interface-card(s), high-speed traces are provided between each exchange-card connector 120 and each interface-card connector 110 and between each exchange-card connector 120 and each transaction-card connector 140. The exchange-card connectors 120 is relatively integratedly distributed in the middle of the midplane 100, and thus the wiring density will be too high in a certain part of the midplane 100, thereby the number of layers and the design complexity of the midplane 100 are increased, and the design cost and the device cost are increased.
If the communication device comprises two frames or a plurality of frames, generally, the communication device still has one unified midplane. Taking a communication device with two frames for example, when the communication device with two frames adopts a structure similar to that of the first type of the midplane, each frame comprises respective interface-card connectors 110, transaction-card connectors 140 and exchange-card connectors 120, which are distributedly arranged respectively in spaces of the midplane corresponding to the each frame. Thus, high-speed traces between the exchange-card connectors 120 in an upper frame and the interface-card connectors 110 and transaction-card connectors 140 in a lower frame cross the upper frame and the lower frame and occupy most of wiring layers, so only quite a few wiring layers on the midplane can be used for allocating power supply. However, due to very large power consumption of a large-capacity communication device, technical means, such as omnibus bars, local wiring, etc., has to be used to resolve a problem of allocating power supply on the midplane, so the design cost and the device cost are further increased.
An exemplary structure of a second type of a midplane is shown in FIG. 2, two sides of the midplane 200 are provided with connectors for inserting cards, wherein the connectors at one side of the midplane 200 are longitudinally arranged and the connectors at the other side of the midplane 200 are transversely arranged. FIG. 2a is a front view of the midplane 200, multiple line-card connectors 210 are longitudinally arranged in parallel with each other at one side of the midplane 200. FIG. 2b is a rear view of the midplane 200, multiple exchange-card connectors 220 are transversely arranged in parallel with each other at the other side of the midplane 200, and multiple management-card connectors 230 are located at the same side as and under the exchange-card connectors 220, and arranged in parallel with the exchange-card connectors 220.
For such a type of the midplane, there is an intersection point between each exchange-card connector 220 and each line-card connector 210, the position of the intersection point differs from other intersection points on the midplane, whereat a high-speed trace connection between the each exchange-card connector 220 and the each line-card connector 210 is completed, so the problem of integrated wiring on the midplane is resolved. However, cards are inserted respectively at both sides of the midplane 200 along completely different directions, so directions of heat dissipation ducts of the midplane 200 are inconsistent. Thus, it is required to provide two distinct heat dissipation systems, one of which has an up-down duct design for longitudinally inserted cards at one side, and the other of which has a left-right duct design for transversely inserted cards at the other side, which makes the design cost and the device cost of the communication devices increased.
Furthermore, since it is required to ensure the connectivity between each exchange-card and each line-card, such a type of the midplane is not applicable to a communication device with two frames or multiple frames, which yields a limitation in the system capacity.